Question

Which of the following cannot show acidic nature?

• A. $H_2{CO}_3$
• B. ${CaCO}_3$
• C. $HCl$
• D. ${HSO}_4^{-}$

Answer 1

The correct option is B

${\mathrm{CaCO}}_3$

The explanation for the correct option (B):

• Acids are the chemical substances that produce Hydrogen ions (${\mathrm{H}}^{+}$) when dissolved in Water (${\mathrm{H}}_2\mathrm{O}$).
• For example, Hydrochloric acid ($\mathrm{HCl}$) is an acid. When $\mathrm{HCl}$is dissolved in Water (${\mathrm{H}}_2\mathrm{O}$), it ionizes to produce ${\mathrm{H}}^{+}$ions.
• $\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{H}}^{+}\left(\mathrm{aq}\right)+{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)$
• When an acid is added to ${\mathrm{H}}_2\mathrm{O}$, then the concentration of ${\mathrm{H}}^{+}$ ions in Water increases, and it will be acidic in nature.
• Calcium carbonate (${\mathrm{CaCO}}_3$) is a salt of a strong base, Calcium hydroxide ($\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$), and a weak acid, Carbonic acid (${\mathrm{H}}_2{\mathrm{CO}}_3$).
• The hydrolysis reaction of ${\mathrm{CaCO}}_3$is:

${\mathrm{CaCO}}_3\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\rightleftharpoons \mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2{\mathrm{CO}}_3\left(\mathrm{aq}\right)$

• Since the salt of a weak acid and strong base gives an alkaline or basic solution, ${\mathrm{CaCO}}_3$is not acidic in nature.

The explanation for the incorrect options:

(A)

• ${\mathrm{H}}_2{\mathrm{CO}}_3$ is a weak acid as it ionizes partially in water to produce ${\mathrm{H}}^{+}$ ions. Hence, it shows acidic nature.
• ${\mathrm{H}}_2{\mathrm{CO}}_3\left(\mathrm{aq}\right)\rightleftharpoons 2{\mathrm{H}}^{+}\left(\mathrm{aq}\right)+{\mathrm{CO}}_3^{2-}\left(\mathrm{aq}\right)$

(C)

• Hydrochloric acid ($\mathrm{HCl}$) is a strong acid. When $\mathrm{HCl}$ is dissolved in Water (${\mathrm{H}}_2\mathrm{O}$), it completely ionizes to produce ${\mathrm{H}}^{+}$ions. Hence, it shows acidic nature.
• $\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{H}}^{+}\left(\mathrm{aq}\right)+{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)$

(D)

• When Hydrogen sulfate ion (${\mathrm{HSO}}_4^{-}$) is dissolved in Water, it ionizes partially to produce ${\mathrm{H}}^{+}$ ions. Hence, it shows acidic nature.
• ${\mathrm{HSO}}_4^{-}\left(\mathrm{aq}\right)\rightleftharpoons {\mathrm{H}}^{+}\left(\mathrm{aq}\right)+{\mathrm{SO}}_4^{2-}\left(\mathrm{aq}\right)$

Final Answer: Hence, option (B) is correct. ${\mathrm{CaCO}}_3$ cannot show acidic nature.